Photodetection of indicia on forms and the like is known. In such systems, a narrow beam of light is focused as a spot or slit of light on the relevant field to be scanned and is moved over the field, either by the deflection of the beam or movement of the form. Light reflected from, or transmitted through, the form is focused on a photocell or other photodetector so that indicia may be detected as variations in the photocell output. Typically, photocell outputs are small so that the photocell is connected to an amplifier and the amplified output is further processed by the system.
One application of photodetection is in the control of inserter systems, which separate and process discrete documents, assemble the documents and other materials into batches to be mailed together and insert the batches into envelopes. Inserting systems are typically controlled according to information, for example "dash codes", encoded on control documents. Dash codes consist of lines, normal to the direction of motion of the printout, which are printed on the control document, typically on the sprocket strips of the printout. The field containing the dash codes is scanned by reflected light as the control document is received by the inserter system and the presence or absence of lines of encoded information defines the operations relating to that control document.
A scanning apparatus used in conjunction with inserting machines having various document feeders is known as an "optical machine reader" or OMR. The OMR requirement for inserting machines has existed for some time and optical scanner technology has developed to satisfy this requirement. For example, in U.S. Pat. No. 4,659,939 issued to John L. Lorenzo on Apr. 21, 1987 and assigned to the assignee of the present invention, there is disclosed an optical scanning system, commonly referred to as an OMR scanner, including an amplifier which automatically adjusts the background reference level and a photodetector which detects light reflected from or transmitted through objects such as code markings on forms. It is well known to use such an OMR scanner in conjunction with document feeders in console inserter systems.
Typically, the scanner is rigidly mounted to the document feeder of the inserter and has to be adjusted in relationship to the sheet being scanned. The physical adjustment to the location of the scanner is a two-way adjustment which depends on the type of material being scanned. In the transverse direction to the paper path, the scanner is positioned over the area in which the dash codes will pass. The second adjustment is to the distance from the sheet containing the dash codes to the lens of the scanner. For both adjustments, the proper positioning of the scanner is essential to ensure the integrity of the scanned information. For inserts, adjustments to the scanner position are usually required whenever the different weighted paper is being scanned or the location of the code on the sheet is changed. Typically, scanner adjustments are expected to be long term and require service technicians to perform the adjustments.
OMR scanners have been used in console inserters, such as the 8300 series inserter of Pitney Bowes, which typically are used to handle large jobs or "runs" consisting of an extensive number of items of the same material with uniform dimensions. As a result, an adjustment of a rigidly mounted scanner by a service technician is not considered to be a problem with console inserters because such adjustments are made infrequently. Generally, once the scanner has been adjusted to a correct position, further adjustments are necessary only when the material being scanned or the location of the control code is changed. Although the OMR scanners perform suitably on the console inserting machines, some of the control codes are missed or misread for various reasons. For example, if the control document is curled or the document is fluttering as it is scanned, the rigidly mounted scanner may misread the control code. Typically, an OMR scanner is designed to scan a certain field of view which requires that the scanned document be within this field of view, such as 0.020 inches, plus or minus a limited tolerance.
Up to now, OMR scanners have seldom been used in tabletop inserters because, typically, tabletop inserters are not used for the uniform, consistent applications such as the console inserters. Tabletop inserters are generally used in limited and variable types of runs, i.e., many runs consisting of different types of material. The use of OMR scanners on tabletop inserters has not been practical up to now because every time the material changes a new adjustment is needed to the position and distance of the scanner to the paper path of the document containing the control codes. However, the requirements for the use of tabletop inserters are becoming more sophisticated and a need for OMR scanning on tabletop inserters is now at hand.